This project is studying the enzymatic assembly of water-insoluble substrates by the liver. Specific examples include the conversion of squalene to cholesterol and the conversion of palmityl-CoA to triglyceride. The conversion of squalene to cholesterol requires both microsomal membranes and at least two sterol carrier proteins. Sterol carrier protein l (SCPl) is required for the conversion of squalene to lanosterol. We are purifying a second sterol carrier protein which is involved in the conversion of lanosterol to cholesterol. BIBLIOGRAPHIC REFERENCES: Scallen, T.J., Seetharam, B., Srikantaiah, M.V., Hansbury, E. and Lewis, M.K. "Sterol Carrier Protein Hypothesis: Requirement for Three Substrate-Specific Soluble Proteins in Liver Cholesterol Biosynthesis". Life Sciences 16, 853-874 (1975). Tormanen, C.D., Redd, W.L., Srikantaiah, M.V. and Scallen, T.J. "Purification of 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase" Biochem. Biophys. Res. Commun., in press Feb. 9, 1976 issue.